1. Field of the Invention
The present invention, in electric vehicles which travel by driving force of an electric motor, relates to a controller for the electric vehicles that is used for determining an abnormality of motor control means which controls the electric motor.
2. Description of the Related Art
In general, an electric vehicle that travels using driving force of an electric motor, as shown in FIG. 8, has an electronic control unit for travel control (travel control ECU) 101 and an electronic control unit for motor control (motor control ECU) 102.
The travel control ECU 101 is constructed to calculate the target driving torque of an electric motor 103 according to information of various kinds, such as an accelerator pedal manipulation signal, a brake manipulation signal, and a shift range signal, by a built-in central processing unit (CPU). The calculated target driving torque is input to the motor control ECU 102.
The motor control ECU 102 is constructed to calculate a final indication torque which has corrected the input target driving torque, based on the operating conditions of the motor 103 and the like, by the built-in CPU.
The motor control ECU 102 is built into an inverter 105, which is constructed to convert the DC power supplied from a battery 104 into three-phase AC power according to the final indication torque calculated by the motor control ECU 102, and supply it to the motor 103. The motor 103 rotates according to the supplied three-phase AC power to travel the vehicle.
In case, some abnormality occurs in the CPUs built in the above-described travel control ECU 101 and motor control ECU 102, the value of the target driving torque or final indication torque will not be normally calculated any longer. Unless the value of the target driving torque or final indication torque is normal, electric power not meeting the travel requests of the vehicle or driver will be supplied, so that there is a possibility that the vehicle will behave against the intention of the driver.
As a conventional technique for detecting the arithmetic abnormality of CPUs built in a vehicle, patent document 1 discloses a technique for providing an auxiliary CPU which detects the arithmetic abnormality of a main CPU separately from the main CPU.
FIG. 9 is a block diagram showing an example of the functional configuration of a simple controller which, in the vehicle explained using FIG. 8, detects the abnormality of the motor control ECU 102 by two CPUs.
As shown in FIG. 9, the motor control ECU 102 has a pair of CPUs, a first CPU (main CPU) 110 and a second CPU (auxiliary CPU) 111 built therein. A target driving torque signal calculated in the travel control ECU 101 is input to both the first CPU 110 and the second CPU 111.
The first CPU 110 has a final indication torque calculator 112 and a PWM drive processor 113. The function of the final indication torque calculator 112 is to calculate a final indication torque based on the input target driving torque, while the PWM drive processor 113 is constructed to supply three-phase AC power from the inverter 105 to the motor 103 so that torque equivalent to the calculated final indication torque is obtained.
The second CPU 111 has a main CPU abnormality determiner 114. The abnormality determiner 114 is set to perform an arithmetic operation equivalent to the arithmetic operation of the final indication torque calculator 112 separately from the first CPU 110, based on the input target driving torque.
The result of the arithmetic operation in the main CPU abnormality determiner 114 is compared with the result of the arithmetic operation in the first CPU 111, and based on the two results, the abnormality of the main CPU is determined.    Patent Document 1: Japanese patent laid-open publication No. 2001-310743